1. Field
The present invention relates to band expanding technologies and, more particularly, to a band expander, reception device, band expanding method for expanding the band of signals.
2. Description of the Related Art
Technologies for expanding a frequency band are sometimes used to output sound in narrow band sound signals (e.g., signals for analog radio systems) and in irreversibly compressed sound signals (e.g., signals for digital sound communication), for the purpose of improving the intelligibility of sound, improving sound quality, and obtaining sound quality less likely to be embedded in a noise. To expand a frequency band, a frequency domain spectrum is generated by subjecting a sound signal to Fourier transform and a harmonic spectrum is generated based on the frequency domain spectrum. The spectrums are superimposed one on the other and the resultant spectrum is subject to inverse Fourier transform (see, for example, patent document 1).    [patent document 1] Japanese Patent Application Laid-open No. 2012-208177
Using Fourier transform and inverse Fourier transform to expand a frequency band enables natural sound reproduction but increases the volume of computation, and, as a result, power consumption. In communication devices such as wireless devices and, in particular, battery-driven mobile terminals, it is desired that the volume of computation required to expand the frequency band be minimized in order to reduced power consumption.